Telephone exchange system



June 9, 1931. H. HOVLAND 8 3 TELEPHONE EXCHANGE SYSTEM Filed Jun e 28.1929 N lNl/ENTDE" w h! HOVLAND ATTORNEY Patented June 9, 1931 UNITEDSTATES PATENT OFFICE HENRY HOVLAND, OF WILLISTON PARK, NEW YORK,ASSIGNOR T0 BELL TELEPHONE LABORATORIES, INCORPORATED, OF NEW YORK, N.Y., A CORPORATION OF NEW YORK TELEPHONE EXCHANGE SYSTEM Applicationfiled. June 28,

This invention relates to telephone exchange systems and moreparticularly to inrprovements in party line message reglstration.

According to this invention a relay is provided in a two-partysubscribers linev circuit for connecting the meter of one of thestations to the tip side of the identification trunk and for connectingthe meter of the other station to the ring side of the identificationtrunk. The winding of this relay is in parallel with the cut-off relayand is operated by booster battery after the called station has answeredand the calling station has been identified. This arrangement makespossible a saving of one or more leads between the identification trunkand the line circuit for operating the message registers.

Another feature of this invention resides in so connecting the componentparts of the subscribers set as to remove the identifying ground duringdialing and thus to make it unnecessary to furnish a pulse repeater inthe identification trunk. This arrangement minimizes the amount ofequipment in the trunk, obviates the necessity of removing pulserepeating equipment when the connection is extended to an operatorsposition and obviates the difficulty experienced in repeating dialpulses through more than one repeater in multi-ofiice areas.

Referring to the drawings, Fig. 1 represents an automatic telephonesystem in which this invention is embodied; Fig. 2 shows an alternativearrangement of the equipment at the stations of a two-party line.

In Fig. 1, A and B represent subscribers stations on a party line, oneof these being a calling station; D represents a called sub c scribersstation; LF represents a line-finder switch which has access to a groupof lines including the line to which the stations A and B areconnected;T. represents a trunk whose associated equipment is arranged inaccordance with this invention to identify the calling station on atwo-party line and to operate the message register which is individualto the calling station; S represents a selector switch which ispermanently connected by the trunk T with the line-finder 1929. SerialNo. 374,357.

switch LF and which is controlled by the actuation of the calling deviceat the calling station to select an idle trunk which terminates at aconnector switch having access to the line of the called station; Crepresents a connector switch having access to a group of linesincluding the line to which the called station D is connected.

The subscribers set at station A is known as the tip subset and isarranged so that the removal of the receiver from the receiver hookconnects an identifying ground 46 to the associated line; this subset isequipped with a special dial so as to exclude the receiver from theconnection to ground 46. V

The subscribers set at station B is known as the ring subset and isarranged so that no ground is connected to the line by the removal ofthe receiver from the receiver hook.

The subsets at stations E and F are similar to those at stations A and Bexcept that the dial at station E is of the same type as the dials atstations B and F and the receiver at station E is included in theconnection to the identifying ground 47. Each of these identifyingground connections is under the control of the ofi-normal springs of theassociated dial, so that the ground is disconnected from the line assoon as the dial is moved oif-normal; this arrangement prevents theidentifying ground from interfering with the satisfactory transmissionof dial impulses when the various digits of a called subscribers numberare dialed. If the identifying ground connection was not opened duringdialing, it would be necessary to provide pulse repeating means in theidentifying trunk circuit to insure proper operation of the stepby stepswitches employed in establishing the by the broken lines which connectto the brushes of these switches.

The line-finder LF, which is represented y brushes 8, 9, and 10 and theassociated terminals, is similar to that disclosed in United StatesPatent No. 1,711,682, issued to HoVla-nd May 7, 1929; the brushes 8, 9and 10 represent one or the two sets of brushes as described in thePatent 1,711,682. The selector switch S which is represented by thebrushes 39, 420 and 4:1 and the associated terminals, and the connectorswitch G, which is represented by the brushes 42, 43 and a l and theassociated terminals.- are of the well known Strowger type similar tothose described on pages 57 to inclusive of the second edition ofAutomatic Telephony by Smith and Campbell.

The operation of a system in which the invention is embodied, asrepresented by the drawings, will now be described in detail. Assumethat a call is ori inated by the removal of the receiver from thereceiver hook at either of stations A or B.

Line relay 2 operates in an obvious circuit over-the line 1 therebyconnecting the winding of the cutoff relay 3 to the sleeve terminalassociated withthe line 1 in the bank of line-finder LF; line'relay 2also connects ground to lead 7 which is effective to cause an idleline-finder to hunt for the terminals of the calling line. During thetime that this line-finder, which we will assume to be the line-finderLF, is hunting for the calling line the sleeve lead 14 of the trunk T isconnected to ground at the front contact of relay 48 in the line-finder,relay l8 having been operated tostart line finder LF. (For a detaileddescription of the operation of such a line-finder reference may be hadto U. S. Patent 1,711,682.) When ground is thus connected to lead 1 1 acircuit is closed from battery through the winding of the identificationtest relay 17, through resistance 16, back contact ofrelay 25', lead 15,normally closed contacts of the continuity springsof relay 33, over lead14 to ground at relay 18 of the line-finder LF. Relay 17 operates inthis circuit and closes an obvious circuit for operating relay 18. Thecircuits for operating relays 17 and 18 are closed-at this time to makecertain that these relays are capable of operating when the calling lineis tested to identify the callingstation after the connection isreleased, as hereinafter described. Resistance16 is equal to or greaterthan the resistance of the longest line to which the line-finder LF hasaccess".

hen the brushes 8, 9 and 10 of the linefinder LF come into contact withthe terminals associated with the calling line 1 a circuit is closedfrom ground relay 48- of the line-finder LF, through sleeve brush l0,and through the front contact of relay 2', to the windings of thecut-off relay 3 and message register control relay l. The cut-off relay3 operates but relay is marginal and doesnot operate until connected toa higher source of potential, as is hereinafter de scribed. The closingof the circuit through sleeve brush 10 is also effective to stop thehunting action of the line-finder. W'ith the brushes 8 and 9 in contactwith the tip and ring terminals of line 1 the line relay (not shown) ofthe selector S is operated in a circuit which includes leads 11 and 12of trunk T, the line 1, and the subset at the calling station. (For adetailed explanation of the operation of the selector S reference may behad to pages 61 to 65 ofthe second edition of Automatic Telephony bySmith and Campbell). Ground (not shown) 'is thereupon connected atselector S over the sleeve lead 19 of trunk T, through the lower windingof relay 20, lead 21 n0rmally closed contacts of the continuity springsof relay 25, lead 15, back contact of relay 25, resistance 16, andthrough the winding of relay 17, to battery. As long as ground atre'l'ay el8 of the line-finder LF is connected to lead 1% of trunk T, ashereinbefore described, relay 20 does not operate for its lower windingis short-circuited by the ground connected to lead 14.-

The operation of the cut-off relay 3 when the line-finder LF finds thecalling line, as hereinbefore described, causes the release of the linerelay 2. The release of relay 2 disconnects ground from lead 7 whereuponrelay l8 releases to disconnect the ground at its front contact from thesleeve brush 10 and from the sleeve lead 145 of trunk T. As a result thelower winding of relay 20 is energized to close its front contacts 22 land 28 without actuating any of its remaining contacts. The circuit forthus partially operating relay 20 is traced in part from the ground (notshown) at selector S, over lead 19' of the trunk T, through the lowerwinding of relay 20, lead 21-, and through the normally closed contactsof the continuity springs of relay 25 to lead 15; from lead 15'onebranch of the circuit is traced through the back contact of relay 25,resistance 16, and winding of relay 17 to battery; the otherbranch istraced from lead 15, through the normally closed contacts of thecontinuity springs of relay 38, lead 14:, sleeve brush 10 of line-finderLE, to battery through the windings of cut-oil relay 3 and messageregister control relay 4 connected in parallel. Relay 17 is heldoperated in the first mentioned branch of this circuit and cut-off relay3 is held operated in the other branch. By the aforementioned partialoperation of relay 20, a third branch of this circuit is closed fromlead 21, through the inner left-hand front contact of relay 18, frontcontact 22 and: upperwinding of relay 20 to battery; the closing of thisbranch is eilective to completely operate relay 20; lVith. relay 20completely operated, ground is disconnected from alarm lead 24 and relay25 is energized in an obvious circuit.

It is apparent that'the complete operation of relay 20 depends upon theprior operation of relays l7 and 18. If relay 18 has failed to operatethe partial operation of relay 2O is effective to operate the alarmcircuit 50 by connecting ground. at the front contact of relay 20,through the inner right-hand back contact of relay 25, to lead 24. Inthis case the closing of the circuit, for operating the callingsubscribers message register, is prevented.

)Vit-h relay 25 operated, as hereinbefore described, relays 17 and 18are released and the alarm lead 24 is transferred to the back contact ofrelay 20. The release of relay 18 does not cause the release of relay 20since the winding and front con tact 22 of relay 20 are now connectedthrough the neXt-to-the-outer right-hand front contact of relay 25, tolead 21. In operating, relay 25 also disconnects lead 15 from lead 21and connects lead 15 to ground through retard coil 26. Thus relay 20 isheld operated in the circuit from battery through its upper winding andfront contact 22, through the front contact of relay 25, lead 21, lowerwinding of relay 20 and over lead 19 to ground (not shown) at selectorS; the cut-off relay 3 is held operated in the circuit from batterythrough its winding, brush 10 of line-finder LF, lead 14, normallyclosed contacts of the continuity springs of relay 33, lead 15, lefthand front contact of relay 25, to ground through retard coil 26. Thisarrangement for holding the cut-off relay 3 operated permits numberchecking on toll calls. The path for the number checking tone from thesleeve brush 10 of the line-finder is traced through lead 14, normallyclosed contacts of the continuity springs of relay 33, lead 15,condenser 27, lead 21, lower winding of relay 20, and through the sleevelead 19 of trunk T to the selector S. No further operation of the trunkequipment occurs until after the connection has been established and thecalled subscriber has answered, as is hereinafter described.

WVit-h the calling lino extended over the trunk T to the selector S theactuation of the calling device at the calling station is effective tostep the brushes of selector S up to the level of a group of trunkswhich terminate at connector switches having access to a group of'linesincluding the called line 45. If the call originated at station A, theidentifying ground 46 is disconnected from the line, when the callingdevice is operated, to insure proper operation of the selector S. Theselector S then automatically selects an idle trunk in the selectedgroup, thereby extending the connection from the calling line 1 throughthe brushes 39 and 40 over th selected trunk to the windings of the linerelay (not shown) of the associated connector switch C. Ground atconnector switch C is then con nected over the sleeve lead of theassociated trunk and through the sleeve brush 41 of the selector S tothe sleeve lead 19 of trunk T, to hold relay 20 operated; the ground atselector S, hereinbefore described as having been connected to lead 19,is disconnected after trunk T has been extended through the selectorbrushes to the connector switch. The connector switch now operates inresponse to the actuation of the calling device at the calling stationto extend the connection from selector brushes 39 and 40 through theconnector brushes 42 and 43 to line 45 which terminates at the calledstation D. (For a detailed description of the operation of the Strowgertype of selector and connector switches reference may be had to pages 57to 65 of the second ed1 tion of Automatic Telephony by Smith andCampbell). The called line having been found idle, a source of ringingcurrent having been connected to the called line, and the calledsubscriber having answered, the source of talking current at theconnector C for the calling subscribers line is reversed, with respectto the tip and ring sides of the line, so as to operate the polarizedsupervisory relay 13 in-the trunk T. The circuit for operating relay 13be traced from battery, through one side of the line relay (not shown)of the connector C,

th-rough'brush 39 of selector S, upper winding of polarized supervisoryrelay 13, co11- ductor 11 of trunk T, back contact of relay 28, brush 8of line-finder LF, over the tip side of the calling line 1, through thesubset at the calling station, ring side of line 1, brush 9 ofline-finder LF, back contact of relay 28, conductor 12 of trunk T, lowerwinding of polarized supervisory relay 13, brush 40 of selector S, andthrough the other winding of the line relay (not shown) of connector C,to ground.

The operation of the polarized supervisory relay 13 closes a circuitfrom ground through the front contact of relay 13, resistance 29, backcontact of relay 31, and through the winding of relay 28 to battery.Relay 28 operates in this circuit thereby disconnecting brushes 8 and 9from conductors 11 and 12 and connecting both brushes through the backcontacts of relay 33, over lead 34 to the winding of identification testrelay 17. Relay 28 is slow to operate so that momentary operations ofsupervisory relay 13 will be ineffective to operate relay 28. Relay 28also closes an obvious circuit for holding relay 25 operated independentof relay 20 and bridges resistance 30 across the conductors 11 and 12 oftrunk T to prevent the release of the line relay (not shown) in con- Citnector C during the test to identify the calling station. Theidentification test relay 17, thus connected to the tip and ring sidesof the calling line 1, is operated if the call originated at station Asince the subset at station A is arranged toconnect the identifyingground 46 to the line when the receiver is removed from the receiverhook. The identification test relay 17 does not operate if the calloriginated at station B for the subset at this station isdistinguishedby the lack of an identifying ground connection.

The operation of relay 28 is also effective to close a circuit fromground through the outer right-hand front contact of relay 25, lead 32,inner lower front contact of relay 28, and through the middle right-handback contact and the winding of relay 31 to battery. Relay 31 operatesin this circuit and looks through its inner right-hand front contact andlead 32 to the same ground, independent of relay 28. If the calloriginated at station A so that the identification test relay 17 isoperated, a circuit is closed by the operation of relay 31 for operatingrelay 18; this circuit may be traced from battery through the winding ofrelay 18, front contact of relay 17, lower front contact relay 20, toground at the inner lefthand front contact of relay 3'1. Relay 18 looksthrough its right-hand front contact to the same ground independent ofrelays 17 and 20. Relay 31 is slow to operate so that the momentaryoperation of relay 17 due to a line charging current will not cause theoperation of relay 18. The release of relay 28, which is caused by theoperation of relay 31, reconnects brushes 8 and 9 of the line-finder LFto conductors 11 and 12 of trunk T so that conversation may behadbetween the subscribers at the calling and called stations. Nofurther operation of the equipment associated with the trunk T occursuntil the connection is released.

When the connection is released by replacing the receiver on thereceiver hook at the calling station, the line relay (not shown) ofconnector C and supervisory relay 13 of trunk T are released. Theselector switch S and the connector switch C are restored to normal inthe usual manner. As a result, ground at the connector G is disconnectedfrom the terminal with which the sleeve brush 41 of selector S is incontact thereby releasing relay in the trunk T. The release of relay 20closes a circuit for reoperating relay 28; this circuit is traced y frombattery through the winding of relay 28, outer right-hand front contactof relay 31, outer lower back contact of relay 20, and through the innerleft-hand front contact of relay 31, to ground. Relay 20 opens thecircuit through the winding of relay 25, but relay is slow to releaseand the operation nects the winding of test relay 17 through brushes 8and 9 to the tip and ring sides of the line 1. But if a foreign groundis connected to the calling line, relay 17 is reoperated to prevent theoperation of relay 33, as is hereinafter described. By preventing theoperation of relay 33, the closing of the circuit for operating themessage register is also prevented and ground is connected through theupper back contact of relay 20 and the inner right-hand front contact ofrelay 25 over lead 24 to operate the alarm circuit 50. v

Assuming that relay 17 does not operate at this time, the operation ofrelay 28 is effective to close a circuit for operating relay 33; thiscircuit may be traced from battery through the winding of relay 33, backcontact of relay 17, inner lower back contact of relay 20,'middleright-hand front contact of relay 31, inner lower front contact of relay28, lead 32, to ground at relay 25. Relay 33, in operating, disconnectsthe ground at retard coil 26 (through the front contact of relay 25 andover lead 15) from lead 14 and connects lead 14 (over lead 38 andthrough the outer left-hand front contact of relay 31, lamp 37 andresistance 36) to booster battery 35. This results in an increasedcurrent through the windings of the cut-off relay 3 and message registercontrol relay 4. The marginal message reglead 14 of line-finder LF whenrelay 33 operated, the connection to booster battery 35 is effective toprevent the release of the line-finder LF.

With relays 4, 28 and 33 operated the message register which correspondsto the station which originated the call, as identified' by the testrelay 17, is operated. If

the call originated at station A, message register 5 is operated in thecircuit from battery through its winding, front contact of relay 4,brush 8, front-contact of relay 28, front contact of relay 33, frontcontact 'ister control relay is thus operated to dis- 1 of relay 18, andover lead 38 to booster battery. It the call originated at station B,message register 6 is operated in the circuit from battery through itswinding, front contact of relay 4, brush 9, front contacts of relays 28and 33, back contact of relay 18, and over lead 38 to booster battery.

The operation of relay 3?), as hereinbefore described, also opened thecircuit through the winding of relay 25 and the consequent release ofrelay 25 opens the circuits through the windings of relays 31 and 33.The release of either of relays 31 or 33 opens the circuits from boosterbattery 35 but since relay 25 is slow to release this circuit was closedlong enough to insure the operation of the calling subscribers register.The opening of the booster battery circuit releases the message registerwhich was operated, releases the message register control relay 1 andthe cut-off relay 3 and also causes the release of the line-finder andthe return of brushes 8, 9 and 10 to normal. The release of relay 31releases relay 28 and also releases relay 18, if previously operated.All of the equipment involved in the connection is now normal.

The invention is not limited in its application to a system whichemployes Strowger type switches and is applicable to all systems whichare arranged for party-line message rate subscribers stations.

What is claimed is:

1. In a telephone system, a line having a plurality of subscribersstations, one of which is a calling station, a message register for eachof said stations, a selector, means including a trunk for extending saidline to said selector, means individual to said trunk for determiningwhich of said stations is the calling station, and means individual tosaid line for connecting said message registers to said trunk.

2. In a telephone system, a line having a plurality of subscribersstations one of which is a calling station, a message register for eachof said stations, a selector, means including a trunk for extending saidline to said selector, means associated with said trunk for determiningwhich of said stations is the calling station, a called subscribersline, means including a connector for extending the connection from saidselector to said called line, a relay operable by a reversal of currentover the talking conductors of said trunk in consequence of the answerof the called subscriber, and means rendered effective by the operationof said relay for operating the register of said calling station overone of the talklng conductors.

3. In a telephone system, a line having a plurality of subscribersstations one of which is a calling station, means said calling stationfor dialing, an identifying connection at said calling station, andmeans for opening said identifying connection during the operation ofsaid dialing means and 'for' automatically closing said connection aftereach opening.

a. In a telephone system, a line having a plurality of subscribersstations one of which is a calling station, means for distinguishingsaid calling station from the other stations on said line, a dial atsaid calling station, a selector, means including a trunk for extending.said line to said selector, a pulsing circuit controlled by said dialfor selectively operating said selector, and means for disconnectingsaid distinguishing means when said dial is moved off normal.

5. In a telephone system, a line having a plurality of subscribersstations one of which is a calling station, a dial at said callingstation, an identifying connection at said calling station, a messageregister for each of said stations, a selector switch, means including atrunk for extending said line to said selector switch, meansassociatedwith said trunk for determining which of said stations is the callingstation, acalled subscribers line, means including a connector forextending the connection from said selector switch to said called line,a supervisory relay operable by a reversal of current over theconductors of said trunk in consequence "of the answer of the calledsubscriber, means rendered effective by the operation of said relay foroperating the register of the calling station over one of the talkingconductors of said trunk, and means for opening said identifyingconnection when said dial is moved off normal.

6. In a telephone system, a line having a plurality of subscribersstations one of which is a calling station, a message registerindividual to each of said stations, a called station, means including atrunk for extending a talking connection from said calling station tosaid called station, means associated with said trunk for determiningwhich of said stations is the calling station, and a circuit whichincludes a single talking conductor of said trunk for operating themessage register of said calling station.

7. In a telephone system, a line, a plurality of subscribers stationsincluding a calling station permanently connected to said line, amessage register "for each of said stations, a called station, meansincluding a trunk for extending a talking connection from said line tosaid called station, means associated with said trunk for determiningwhich of said stations is the calling station, a circuit including oneof the talking conductors of said trunk for operating one of saidmessage registers, and a second circuit including the other talkingconductor of said trunk for operating another of said message registers.

l 8. In a telephonesystem, a 1ine,-a-plura1- ity of subscribers stationsincluding a calling station permanently connected to said line, a dialat said calling station an iden- 5 tifying connection at said callingstation, a message register for each of said stations, a called station,means including a trunkior extendingv a talking connection fromsaidcal-ling station tosaid called -station,means 16 associated with saidtrunk for testing said linertodeterminewhich of said'stations is thecalling station, a circuitincludin'g a single talking conductor ofsaidtrunk for operating that one of said message registers whichisindividual to said calling station,

and means for holding said identifying connection openduring theoperation of said dial.

9. ,In a telephone system, a line having a 20 plurality of subscribers:stations one of which is a calling station, a receiver and receiverhook at said calling station, an identifying connection at said callingstation closed by the removal of said receiver from said receiver hooksaid receiver being-excluded from said connection,:a dialing .device atsaid calling station a called station, means including a trunkrforextending "a connection from said calling station to said calledstation, means "individual to said trunk for testing said line todetermine which of said stations is the calling station, and means foropening said identifying 0011-. nection While saiddiali-ng device isbeing operated.

' In Witness whereof, I hereunto" subscribe my name this 23d da0f-'Ma-y,v1929. I

. H NRYH-OVLAND.

